The present invention relates generally to drive systems for powering electric motors, and more particularly to a modular drive system designed and adapted for controlling motors of various sizes and ratings.
A myriad of applications exist in industry for electric motors of various types. In many applications, induction motors are driven to rotate loads, such as pumps, fans, and conveyors, to mention only a few. Other types of motors may similarly be driven. A load may call for uniform speed and torque throughout its life, although many applications require much more flexible control. That is, a motor may need to be driven at different speeds and with different torques at different stages in its operation. To accommodate such needs, variable speed motor drives have been developed that allow for output waveforms of varying and controllable frequency, capable of correspondingly varying the speeds of driven motors. Similarly, equipment has been developed for soft starting motors, starting and stopping motors in controlled manners, and so forth. Such motor drives are now ubiquitous throughout industrial, commercial, shipping, material handling, and other applications.
In general, motor drives are designed to provide good service life in a range of conditions and with a range of loads. The drives may be designed around a single package that can be programmed and wired to receive input power as well as to output conditioned power to the electric motor. Such packaged products typically include power conditioning circuitry that receives alternating current (AC) input and converts the AC input to a direct current (DC) form, before reconverting the DC power to controlled frequency AC output. Various operator interfaces and programming platforms may also be provided, as well as networking capabilities.
One particular challenge that arises in such products is the design for various motor sizes, for facilitating programming, for sharing programming and control parameters, and so forth. Most such products have been designed to power specific sizes of motors (typically rated by the power output or frame size), and the user must select and program the appropriate product for the particular motor to be powered. All of the circuitry used to control power electronic devices within the drives has typically been included in the single package. Programming has been done either manually or by an interface with a configuration computer or network connected to the unitary package. This product paradigm, however, suffers from drawbacks including limitations of installation and configuration of the drives, relatively inefficient use of control platforms between drives, in accessibility of the programming once the drive is commissioned, or, conversely, risks of access to the drives from exterior sources due to resident network connections.
One novel approach now being taken for motor drives involves design and construction of “modules” that are interfaced to provide the desired control and power. In some such designs, control modules or sub-assemblies are paired with power modules or sub-assemblies, with communication between the two, once interconnected, to provide the desired control signals for the power components, and to provide feedback for the control components. Some designs incorporate native or integrated communications circuits that allow for communication with external or remote devices, such as for programming the drives, altering settings, monitoring operation, or communication and coordination with other drives. However, such designs generally do not allow for retrofitting or optional incorporation of such communications hardware, firmware or software.
There is a need, therefore, for improved techniques for driving electric motors that can respond to such drawbacks.